Nowadays, container ships have become larger in size with rapid development of the container transportation system in the international routes. This accordingly demands an increase in the loading and unloading efficiency of the port loading and unloading apparatus (a quay crane, a yard crane or the like) configured to load and unload freight onto and from a container ship. In addition, the society's attention to environmental issues urges energy saving measures for reducing CO2.
Against this background, an apparatus has been provided which includes: a hoisted cargo holding torque calculator configured to calculate hoisted cargo holding torque needed to hold a hoisted cargo on the basis of the weight of the hoisted cargo; a maximum torque calculator configured to calculate maximum torque which a motor configured to wind up and down the hoisted cargo is capable of outputting; and a controller configured to control acceleration of the motor within a range of torque for accelerating the hoisted cargo which is obtained by subtracting the hoisted cargo holding torque from the maximum torque (see Patent Document 1, for example).
This apparatus reduces the cycle time by reducing an amount of time taken to wind up and down the hoisted cargo. As a result, the apparatus is capable of reducing an amount of time taken to load and unload freight, and accordingly its energy consumption.
Meanwhile, the port loading and unloading apparatus includes: main equipment for performing main operations such as loading and unloading work; and auxiliary equipment which is equipment other than the main equipment, and which includes a cooling device for cooling the main equipment whose temperature rises due to heat generated by the loading and unloading work, and a room of the port loading and unloading apparatus, as well as a lighting device for lighting a loading and unloading operation range in order to avoid danger which is involved in work in the dark.
Such auxiliary equipment, such as the cooling device and the lighting device, constantly works while the port loading and unloading apparatus is in operation. Power consumption of the auxiliary equipment accounts for as large as approximately 30% to 60% of overall power consumption of the port loading and unloading apparatus. To reduce electric power to be consumed by the port loading and unloading apparatus, therefore, power consumption during the main operations of the port loading and unloading apparatus needs to be reduced by improving the main operations, and power consumption of the auxiliary equipment also needs to be reduced.
However, the aforementioned apparatus is capable of reducing electric power to be consumed during the main operations, but the apparatus does not reduce electric power to be consumed by the auxiliary equipment.